Commit 7e406d1f authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

sched: Avoid double preemption in __cond_resched_*lock*() 



For PREEMPT/DYNAMIC_PREEMPT the *_unlock() will already trigger a
preemption, no point in then calling preempt_schedule_common()
*again*.

Use _cond_resched() instead, since this is a NOP for the preemptible
configs while it provide a preemption point for the others.

Reported-by: default avatarxuhaifeng <xuhaifeng@oppo.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/YcGnvDEYBwOiV0cR@hirez.programming.kicks-ass.net
parent a315da5e

kernel/sched/core.c

+3 −9
Original line number Diff line number Diff line
@@ -8218,9 +8218,7 @@ int __cond_resched_lock(spinlock_t *lock) 


	if (spin_needbreak(lock) || resched) {

		spin_unlock(lock);

		if (resched)

			preempt_schedule_common();

		else

		if (!_cond_resched())

			cpu_relax();

		ret = 1;

		spin_lock(lock);
@@ -8238,9 +8236,7 @@ int __cond_resched_rwlock_read(rwlock_t *lock) 


	if (rwlock_needbreak(lock) || resched) {

		read_unlock(lock);

		if (resched)

			preempt_schedule_common();

		else

		if (!_cond_resched())

			cpu_relax();

		ret = 1;

		read_lock(lock);
@@ -8258,9 +8254,7 @@ int __cond_resched_rwlock_write(rwlock_t *lock) 


	if (rwlock_needbreak(lock) || resched) {

		write_unlock(lock);

		if (resched)

			preempt_schedule_common();

		else

		if (!_cond_resched())

			cpu_relax();

		ret = 1;

		write_lock(lock);